Firefox memory leak investigation Kibana 7.6

[marius-dr]

This is sort of a large meta investigation issue on Kibana's browser memory usage.
Started after the Kibana CI tests were running in to "Out of memory" errors during the Firefox tests.
Initial runs show a big disparity between Firefox and Chrome, but more important is the slope of the graph for VSZ, as it keeps going higher for Firefox, compared to the uniformity for Chrome.

Older Firefox version shows a lower all around usage, but there is still an increase so this points to a memory leak of some kind.

The difference between the firefox versions can be sort of explained by this issue: https://bugzilla.mozilla.org/show_bug.cgi?id=1608501

What we've looked into until now:

• the Memory tab in Firefox: it looks like the snapshot it takes is only of the RSS memory, so it won't help very much here.
• the about:memory tool: pretty complicated to figure out, but it might be worth using more unless we find a better tool.

What's planned to do (unless we get better ideas):

• run the Kibana functional tests per each app, 10 times each and see which has the largest increase between start and end.
• run about:memory at the start of the tests, run it at the end as well and then compare the two saved results manually

How we've tested it until now:

• setup Metricbeat on a machine in order to gather the usage data for Firefox during the run
• run the Firefox tests:
  node scripts/functional_tests_server.js
node scripts/functional_test_runner.js --config test/functional/config.firefox.js
• look at the logs from Metricbeat in another Kibana instance (I've used a cloud one in order to not influence the run).

[elasticmachine]

Pinging @elastic/kibana-qa (Team:QA)

[elasticmachine]

Pinging @elastic/kibana-operations (Team:Operations)

[LeeDr]

Here's the commit where the tests were disabled. fe38642
I don't see any other issues showing logs from the Jenkins failures. We might have to create a PR to turn the Firefox tests back on to capture details.

[marius-dr]

Over the weekend I ran each test suite from the functional tests 15 times in order to narrow which area causes the most trouble on Firefox:

1. Dev console tests. Everything looked decent, within the parameters.

2. Getting started tests. Good.

3. Log Context tests. Huge spike there.

4. Dashboard tests. Some spikes but acceptable.

5. Discover tests. Going up consistently, not very good.

6. Home tests. This was the worst of all, memory usage kept going up and up until it crashed with a `Detected an unhandled Promise rejection. out of memory"` error

7. Manangement app tests. All good.

8. Status page tests. Too small to be relevant.

9. Timelion tests. Decent. (should be changed to Timelion viz tests as the app should be going out soon).

10 Visualizations tests. Some increases, but incredibly long test, so I think it fared average.

[lizozom]

Closing this issue due to inactivity.
Feel free to reopen if needed 🙏🏻